Question: $ { \left[\begin{array}{rrr}{2} & {1} & {1} \\ {-1} & {3} & {1}\end{array}\right]-\left[\begin{array}{rrr}{-2} & {4} & {-1} \\ {2} & {-1} & {-2}\end{array}\right] = {?} } $
Solution: To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{rrr}{2}-{-2} & {1}-{4} & {1}-{-1} \\ {-1}-{2} & {3}-{-1} & {1}-{-2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{4} & {-3} & {2} \\ {-3} & {4} & {3}\end{array}\right]}$